1. Field of the Invention
Polyphenolic condensation products (namely polyphenolic condensates or PNX), epoxidized products thereof (namely multi-functional epoxy resins or MFE), their process of manufacture, and their applications are disclosed. It is an aim of the embodiments of the instant disclosure to reduce Color (Gardner Index) and to increase ultraviolet (UV) absorbance (340-370 nm, especially 350 nm and 365 nm) of PNX (mixture) and MFE (mixture), which are used in electrical laminates, such as copper clad laminate (CCL) or printed circuit board (PCB) as a UV blocker for photo-lithographic processes.
2. Description of the Related Art
Polyphenolic condensation reactions are described in U.S. Pat. Nos. 5,012,016; 6,001,950; 6,140,421; 6,232,399; 6,316,583; 6,201,094; 6,239,248; 6,379,800; and 6,608,161 and United States Published Application 20110098380. Commercial polyphenolic condensation products (PNX) are available under the trademark/tradename Durite SD-357B from Hexion (Borden Chemical) and TPN1 from Nan Ya Plastics. Epoxidization reactions are described in U.S. Pat. No. 6,201,094 (Example 8) and U.S. Pat. No. 6,001,873. Commercial multi-functional epoxy resins (MFE) are available under the trademark/tradename EPON 1031(A70) from Hexion (Borden Chemical); XB-4399 from Huntsman; 1031(A70) from Shell; TNE190A70 from Chang Chun Plastics. Applications of PNX and/or MFE in flame retarding compositions are described in United States Published Application US 20080064792, U.S. Pat. No. 7,662,902 and PCT application WO2016141257. The disclosures of the above referenced patents and publications are herein incorporated by reference.
A typical multilayer PCB process can be illustratively found in FIG. 1. PNX and/or MFE provide not only good thermal properties, but also good optical properties. The high UV absorbance (340-370 nm) avoids a possible damage on the other side of the PCB (Compare FIG. 2A with FIG. 2B) during the photolithographic process, especially for thin-layer or multilayer circuit boards.
It has been found that the PNX and the MFE produced therefrom are high in UV absorbance, but they are too dark in color for visual-light or UV-light AOI system, resulting in low recognition of printed circuit from epoxy resin substrate. In another aspect, some products are light in color, but too low in UV absorption/blocking for PCB etching process, resulting in ghosting images printing through from the UV light applied through a mask during PCB production. It is difficult to produce PNX and MFE produced therefrom with properties of light color and high UV absorbance.
Thus, there exists a need for improved polyphenolic condensation products (PNX) and multi-functional epoxy resins (MFE) produced therefrom for use in PCB production as well as AOI system.